Hi guys
already for some time I am experiencing this issue. Since I really want to use my second monitor I was forced to write this
Looks like I am not alone, since in other (Linux) forums have the same(similar) issues.
To be honest I am using Solaris express, so definitely not S10, but it should work too ...
it's S11 build 31 and after trying to run the default xorg.conf I get the NVIDIA splash, X starts, but then ... X is frozen (system works, so login through ssh works and you can restart X/troubleshoot)

Hmm, did help a little bit
it did freeze like 2 min. later than before this BIOS upgrade & I even got the gdm started up, but then dead again
The logs are slightly different too, there are mainly Head, not so many Channel warn msgs.

I've not explicitly tested a GeForce FX5200 in Solaris, as only Quadro cards are officially supported in Solaris. I have successfully setup TwinView and two X screens in Solaris with several different AGP Quadro cards.

I tried another thing, setting up nvagp to 0 ... got a little bit further ... gdm seems to be working ... slooow, but working
But after I try anything that has to draw something or such stuff, it's slow